Grease resistant paper



Patented Feb. 7, 1933 THEODORE I. BRADLEY, O1 WIBTFIELD, NEW JERSEY,

cues]: nasrsrm runs.

80 Drawing.

This invention relates to ease resistant carton board and process making same, and relates particularly to grease resistant aper products intended for use with greasy 5 oodstuffs and other similar articles.

In the preferred form ofmy invention I.

provide a coating solution or composition for carton board which is almost non-volatile at ordinary room temperature, that is, at a 1 roximately 70 F. and' yet which dries quic y at slightly elevated tem eratures, for example, at about 140 F. his is of particular importance where liquids of alle ed toxic nature, such as, for example, benzo are employed, and also when im roved flowing and 7 working qualities are desirable. One of the features of the present invention comprises a method for reducin and, in fact, practicall or substantially e iminating all evaporat1on of benzol at ordinary room temperatures (6570 F.) from nitrocellulose solutions, although not preventing the evaporation when the temperature is elevated, such as when the coated materials are exposed to a 5 mild heat as by bein quickl passed through ovens, equipped wit venti ating devices or solvent recovery systems. It is suflicient to .s hicles are rather costly, and, furthermore, have the disadvantage of being somewhat too slow drying, even when the materials are oven dried. Under the present invention 1 much less ex ensive and generally more satisfactory res ts.

Applicationmea Anrnlt :1, 1027. serial No. 818,781.

This invention, in the embodiment which I consider mostpracticable at the present time, involves the use of coatin compositions preferabl containin nitroce lulose and a oompatib e resin or alsam and having a solvent vehicle for nitrocellulose easily vola tile at ordinary room temperatures, preferably with a diluent of like or the same general' range of volatility, together with such a percentage of a wax as will. prevent appreciable evaporatlon of said solvents and yet yield a surface finish substantially free from rings, ock marks, waxy finish, or other such irregu arities co monly' caused by excess wax. It has been ound that waxes such '9 as Japan and carnauba waxes are of but little value in accomplishing the object of this invention, except as they may exert a polishing effect; the most satisfactory results having been secured from mineral waxes, either 95 paraflfin or ceresin wax or ozocerite. Furthermore, definite proportions have been determined, the use of, substantially ater amounts than those stipulated 'ten mg to reduce the gloss of the coatings and to pro- I duce rings, pock marks, waxy surfaces, and various other surface irregularities, while the use of substantially lesser amounts do not satisfactorily checkevaporation at room temperatures. I Thus a nitrocellulose and resin coating composition may be made as follows:

Example 1 Rosin ester 40 Dibutyl phthalateunf L w viscosity. nitrocellulose p 75 Butyl aceta Toluo v Ethyl alcohol I 8O Ceresin wa i B I This com contains solvents ofmediumvolati 'ty, does not dryreadily at or- 90 dinary room temperatures, and yet has been found to dry very ragidly when surfaces coated with it are place in an oven at about 120 to 140 F. The composition has been found to dry to a flexible and glossy smooth surface. In manufacturing such a composition the wax and resin may be dissolved in a portion of the solvent mixture and blendedrosin phthalic lxceride resin, Congo r0511! phthalic -glycer1de' resin, castor oil phthalic glyoeride resin, and also a special type of resins produced from cottonseed oil fatty acids, phthalic anhydride and glycerol. Although as aforesaid, various resins may all be employed in the grease resistant compositions of this invention, it is advantageous.

and usually referable to employ a resin which is inso uble in fatty oils and greases. In fact, in case such a resin is employed, it is often possible to utilize only this resin as a greaseproofing agent, it being then not always necessary to emplo vnitrocellulose or.

other cellulose ester, A suitable resin for this work is that which may be made by slowly heating 50 parts by weight of glycerol, parts by weight phthalic anhydride and 45 parts 1) weight of the fatty acids of cottonseed oi to a temperature of'47 5 F. Since this resin is somewhat soft, it is preferably used in combination with nitrocellulose when non-tacky surfaces are desired. Compositions may contain the various types of plasticizin agents such as castor and rapeseed oils. 11 some cases all resin may be omitted. Various other'tlypes of plasticizin agents maybeemploye ,or mixtures thereo ,amon

which are castor and rapeseed oils, dibuty and diethyl* phthalate, tricresyl phosphate, .camph0r and other nitrocellulose softening or plasticizing agents. Pigments may be employed if colored surfaces are desired.

arious. solvents may be employed in the roduction of the grease-res1stant carton oard. All of the usual nitrocellulose solvents of a low or medium volatility may be employed, it merely being necessary that said solvents or mixtures thereof have suflicient solvent action on the wax to maintain the same substantially in solution; suflicient to function in the manner aforesaid. Thus, either ethyl, propyl, butyl, amyl and hexyl acetates or 'propionates may be used, in some cases alone, or more preferably in admixture with various alcohols or h drocarbon diluents of like degree of volatility. Other nitrocellulose solvents suchas acetone, ethyl .methyl ketone and similar volatile solvents may likewise be employed to produce satisfactory solvent vehicles.-- The pro ortion of wax may be altered-slightly, acco'r in to the solvent mixture employed, although it is in all cases necessary that sufficient wax be used to render satisfactorily slow drying at room temperatures, while avoiding the use of such excessive amounts as will disrupt the surface finish. This will vary slightly according to the solvent mixtures employed and also according to such variations in room temperature as may obtain. In general, it is not advisable to employ substantially over 2 per cent (on the weight of the solvents employed) of parafiin or oeresin wax. A large proportion of wax, as stated, tends to produce defective surface finishes. to use m'uch less than of 1 per cent of said waxes. to good advantageinsome cases.- The use of alcohols have been found of some value the proportion of wax is not confined to very narrow limits. Whereas, in my compositions a limitation is placed on the wax con-' tent such as to avoid surface defacement. In my compositions the wax preferably is maintamed almost entirely in solution or dispersion through the aid of the nitrocellulose functioning as a protective colloid. F urthermore, the present application relates to compositions which are intended for coatin purposes, whereas the aforesaid paint an var-- nish removers are intended for the removal of coatings. In other words, my composition is intended for a totally different purpose than paint and-varnish remover and is, moreover, prepared with respect to consideration of a character totally different from those obtaining in meeting the requirements of 1paint and varnish removers.

' n the preferred form of my invention I employvolatile solvents which do not leave any disagreeable residual odor on paper survent such as acetone may be employed, it is preferable to use a composite one comprising Nor is it advisable Less wax can be used in cold weather faces treated therewith. While a single sola mixture ofnitro'cellulose solvent and wax solvent and containing a proportion of wax very slight with respect to the total amount pf the composition, at sufiicient to substantially prevent evaporation at 70 F., but not materially preventin evaporation at'a temperature somewhat a ove 100 F.

To secure a maximum degree of wax-dis persing effect with a minimum of wax-expulsion with the object of eliminating surface defacement by the wax, I preferably employ low viscosity nitrocellulose such as a grade above one second and below four second material. Low viscosity nitrocellulose has a desirable cooperating action with the mineral wax or other wax employed. With such low viscosity nitrocellulose I may use a more effective concentration of wax and still keep the proportion of wax below a surface-defacing V concentration. This may be due to. some species of protective colloid action or to other causes. Employment of low viscosity nitrocellulose in conjunction wiih a modicum of wax in compositions intended for coating, constitutes a feature of the preferred form of my invention. An ultra-low-viscosity nitrocellulose such as one-half second or one-tenth second may, be used in some cases.

I have set forth paraflin or ceresin wax in the preferred compositions, and in general, have preference for a mineral wax; ceresin, because of its amorphous character being of particular value from the .standpoint of effective dispersion and adequate proportion at-a concentration approaching the surfacedefacing point. Beeswax and other. waxes or mixtures of waxes, e. g., a mixture of beeswax and ceresin wax having properties like, or approaching the mineral waxes as set forth herein are included within the purview of my invention, which embraces substances, a modicum of which greatly reduces evaporation of the unitary or composite volatilesolvent vehicle at room temperatures while permitting free escape thereof at slightly elevated temperatures. The proportions in the illustrative example may be varied and the components altered in grade or quality as desired within wide limits (except as regards proportion of Wax, as has been described) Some of the components are not essential at all times. and plasticizer, for example, ma be omitted in some cases. The resinous b0 y likewise may be omitted if a pronounced gloss or strong adhesionis not needed. The foregoing has largely been derived from my co-pending patent application Serial No. 183,011 and constitutes a continuation in past of the same.

Paper of various kinds such as manila, kraft, sulphite, tissue, glassine, carton board, and other types of paper are all subject to treatment by the process and with the compositions herein disclosed, in order to render them substantially grease resistant and thus enable greasy food products to be contained therein without exudation of grease. The composition suitable for such use comprises either aease-insoluble resin alone or more; preferabg in admixture with nitrocellulose, acetyl cellulose, nitro-acetyl cellulose. cellulose ethers and/or organie-solvent-solublc cellulose compounds. When such'cellulose compound is employed it is possible to incorporate other resins which are soluble in grease in small proportions, although if a grease-insoluble resin such as the cottonseed phthalic glyceride synthetic resin is employed in admixture with nitrocellulose, it is possible to utilize very much larger percentages of the said grease-insoluble resin than of a grease-soluble resin. Thus, the composition utilized in the present invention embraces bodies which are substantially insoluble in grease or fatty oils, whether comprising a cellulose ester or a grease-insoluble resin. Utilizing either or both of these types of materials one may add thereto small proportions of grease-soluble materials as softening or extending agents without serious trouble.

' Ewample 2 A composition containing a grease-resistant resinis the following:

' Parts by weight Low voscosity nitrocellulose"-.- 40 Cottonseed phthalic glyceride resin 40 Dibutyl phthalate 20 Ethyl acetate 135 Benzol 135 Parafiin wax 5 The paraflin wax is dissolved in a portion of the solvent vehicle and the nitrocellulose and synthetic resin are dissolved in other por- I tions of the sol-vent vehicle, then admixed to form the finished coating composition. This may be thinned with the same solvent mixture to any desired extent, the exact amount of total solids being regulated to deposit the particular thickness of grease resistant coating desired. The composition may be applied by any suitable means to the paper which is to be treated. For the best result it is preferable to employ a paper having a surface easily impregnated and in some cases to secure the best impregnation it is desirable to conduct the coating operation under pressure. Ordinarily, however. the paper may be run over rolls or through a bath of the material being coated on either one side or alcohol, etc. It is desirable to employ only such solvents as may be readily eliminated from the coated article and which do not leave any residual odor to contaminatethe paper so treated.

' suitable. for grease-proofin material and It has been found that coatings of this type are extremely resistant to penetration by oils and greases and also have a waterproofing action as well and that it is necessary to have a very good impregnation of the surface for proper protection. Very thin coatings of suc degree of thickness that they can hardly be neasured with (a; (inicrometer are often satis actory, provi e proper impregnation has been obtained. Surface coatings of great thickness are not usually so desirable, often .bein porous and of such different degree of exibility from the paper that they often crack upon bendin and separate from the paper surface. hin layers show better adhesion to the paper surface and a greater degree of flexibility for a given composition than heavy papers. It is thus considered that a coating is not of optimum character unless a very thorough filling of the interstices between the surface fibres has'been accomplished.

In order to produce a proper type of surface impre um it has been oun desirable, as indicatedTto sub'ect the coated paper surface to the action 0 hot calender rolls. This is particularly eflicient when the composition contains resin and plasticizing agents in admixture with the cellulose ester. The hot calender treatment induces a superimpregnation of the fibres and tends to close up pores develo (1 during the evaporation of solvents from tii: coating composition, thus increasing the resistance to seepage by grease.-

Papers treated w.th a surface impregnum of the compositions disclosed herein may be readily fabricated to form paper 'cups boxes, cartons, and other containers for foo products. It is often advantageous to impregnate onl one side of a paper, this being then cutan folded to form containers in which the impregnated rease resistance surface forms the interior 0 the container fabricated therefrom. Such a container has been found to be suitable for the packing and transportation of The invention therefore involves a medium 4 g palper comprising substantlally a grease-mso uble coating a com osite solvent vehicle therefor. The inventlon further involves a composite solvent vehicle comprising solvents which are ordinarily very volatile but containing' a modicum of wax which greatly resoluhlematerial as thezbasic in r may'contain lasticizers and various extend ing agents.

duces the evaporation of the solvent at room temperature, while rmittin evapora; tion thereof at slight y eleva temperatures. As heretofore statedfthe grease resistant ma- .terial employed most com a?" ase-in- With e invention is concerned reas food products such as bacon, butter,- lar% an other greasy articles.

"as and the process of hot calendering a paper carrying a cellulose ester surface impre um resistant tov penetration by oils an greases whereby increased resistance to said penetration is obtained. The invention comprises not only pa or carrying a surface impregnum of sai grease-res:stant.materials but also pa r containers (cartons and the like) made t erefrom. p

Ewaml 3 Parts by f weight Nitrocellulose 30 Cottonseed phthalic glyceride resin 160 Acetone 250 Mineral wax 2 Example 4 Parts by weight Nitrocellulose (low viscosity).; 40

Cottonseed phthalic glyceride resin 400 Ethyl acetate 200 Acetone 200' Benzol r:. 300 Wax 15 Owing to the high proptrtion of resin in Examples 3 and 4, it may be necessary to pass the coated aper over a hot plate immediately before fol ing into cartons, since the heated paper may be bent to better advantage than when cold. Preheating before folding allows of the use of a tion of resin.

If the resin were ndtgreaseroofso high ,a proportion would be unsafe wlth a grease-resistant resin of the type specified in Examples 2, 3 and 4., s

In a similar manner-peanut oil phthalic glyceride may be'employed in Examples 2, 3 and 4 in complete replacement or partial substitutio'n of the cottonseed roduct.- I

The glycols, such as ethy ene or ropylene glycols may be used to form synt et1c balsams which are appropriate for use with nitrocellulose especially in conjunction with resins of the type particularly noted above. Thus I may employ for coating the carton board the following:

realtively high proporut is feasible a I Ewamplefi Parts by Nitrocellulose (l-second viscosity) s 20 Soya bean oil benzoic glycol balsa'm 35 So vent mixture (ethyl acetate and benzol ..200

Para wa 2 tCeresin wa v e 2 -Eoampl e'6 Tothe composition of Example .5 add 50 parts cottonseed phthalic glyceride and sumcient solvent to render of proper coating con- .sistency. v

Example 7 contains a balsam of a different type, being made from a glycol-ether.

Emample 8 Parts by weight Cellulose acetate 10 Compatible glycol-ether balsam 20 Solvent as in Example 7 200 Paraflin wax 4 This composition may be used when the mflammability of nitrocellulose is considercd a hazard.

Ewample .9 p

Parts by weight Nitrocellulose (high viscosity) l0 Rosin cottonseed phthalic glyceride resin Tricresyl phosphate 10 Precipitated magnesium hydrate 10 Hydrated calcium sulphate 15' Solvent as in Example 7 200 Paraflin wax 4 A coating of greatly reduced inflammability is secured y high resin content, use of tricresy-l phosp ate as a plasticizer and employment of, hydrated inorganic bodies. The In esium and calcium com ounds used in the a ove example have'very s ight hiding power, hence being of low yield a coating that is practica if so desired.

Resins and balsams made with a phthalic component have been referred to frequently in the foregoing for the reason that phthalic acid or anhydride is readily obtainable cheaply in abundant quantities and lends itself to resinification readily, but such illustrative use of a desirable commerciall -feasible form of resin is not to be construe as limiting the invention in an way as numerous ot ier acids and anhydri es such as diphenic,

1y transparent terephthalic, salicylic, benzoic, chlor benzoic,

nit-r0 benzoic, malic, maleic, succinic, sebacic, and the like, may be emloyed in producing a grease-resisting resin for the purposes of the present invention.

The process oft-he invention is illustrated as follows: I

. Example 10 Carton board is fed from a roll through a coating device containin a coatin composi-' tion such as is set forth a ove. 0n y one side pigment value tion is removed from the surface by means of a scra er or doctor and the web travels throng the temperature is maintained at 135140 F. An exhaust pump or blower attached to the hot chamber withdraws the solvent vapors. The web then passes to a hot roll or calender .where the final surface solidification or compacting occurs. In this step any traces of residual solvent depart after having assisted in slightly softening or fluxing the surface impregnum, to the extent necessary to consolidate and integrate such impregnum. By'

carrying out the calendering at a temperature above the melting point of the wax, the latter tends to fill any porosities of the-surface and assists in waterproofing the paper.

a steam-heated chamber in which This is of especial importance in the case of foods such as butter, mayonnaise and various emulsion products, as grease-resistance and.

water-resistance are required. The wax also acts as a lubricant, permitting the hot-calendering to proceed smoothly.

By theuse of wax, the firehazard from the employment of volatile inflammable sol vents is greatly reduced, but in some cases the solvent itself must be of a slightly in 0 fiammableor non-inflammable character. To

meet this requirement paper may be coated as follows Example 11 Parts by weight Low viscosity nitrocellulose 40 Cottonseed phthalic glyceride resin 40 .Tricresyl phosphate vCarbon tetrachloride 10-0 Butyl acetate 170 Paraffin wax -Q 5 The preferred form of finished carton board carries a scarcely-visible, flexible,-

grease-resistant surface impregnum comprising a cellulose ester, a grease-resistant subreduce volatility of solvents for the composigradients being in amounts sufiicient to give grease repellent properties to the paper;

3. Glassine paper as defined in claim 1 in which the coating has been subjected to hot calendering subsequent to its application.

4. Qiessme paper carrying a coating as defined in claim 2 in which the coating has been hot calendered subsequent to its application.

'5. Glassine paper carrying a coating of. a composition consisting rimaril of nitrocellulose, wax and polyhy ric alco ol-polybasic acid resin, the ingredients being in amounts sufiicient to give substantial grease repellent ing mi amounts sufficient to give substantial grease re ellent properties to the paper.

8. A g assine wra ping paper for covering ea articles, sai paper carrying a coatmg 0 a composition consisting primarily of nitrocellulose, paraflin wax in an amount sufficient materially to reduce volatisllig of solvents for the composition but in cause substantial blemishing of the composition, and polyhydric alcohol-polybasic acid resin, the mgre ients bein in amounts sufficient to give substantia grease re ellent' r perties to the aper, the coating aving been hot calendere subsequent to its application.

9. Glassine paper for wrapping greasy articles, sand paper carryin a coating of a composition containing cell ose ester, paraffin wax in an amount suflicient substantially to reduce volatilityof coating composition solvents but insuflicient to cause substantial means a polybasic acid resin and mineral wax, the materials being present in an amount suflicient to impart substantial grease repellent properties to the pa er, the wax bein presentin an amount su cient to reduce v0 atility of solvents for the coating composition, but being in an amount insuflicient to cause substantial blemishin of the coating.

v THEO ORE F. BRADLEY.

cient to blemis of the coating, and lyhdric alcohol-p0 ybasic acid resm,.the. I 1 0 onto beingin glelfiunts suflicient togg'lesu tihal greasere e nt ro festo e a e coatin com 'tibn avingbeensu imam j .withamater hot. c endermg subsequenttd ita app cation. 10. A covering for a containing are 'ticleconsist' =-of a a r which is i ficon'sist ing primarily of iiitroe cellulose admixed with a polyhydric alcohols l ybasic acid the materials ar sl mt m of: a

paper which with'amateri co present in'an amount'sufllcient toim substantial 111.. e'overingfor agreaaecontuinmg a'r- 'ticleco scouted ns1st1ngprimanlyonitro cellulose admixed with a polyhydric alcohol- 

